Aluminum alloy brazing sheet and method for manufacturing the same

ABSTRACT

An aluminum alloy brazing sheet used for brazing in an inert gas atmosphere without using a flux includes a brazing material cladded onto at least one side surface of a core material. An oxide is formed on a surface of the aluminum alloy brazing sheet by brazing heating, the oxide including any one or two or more of Mg, Li, and Ca and having a volume change ratio of 0.990 or less to a surface oxide film formed before brazing heating, and an atomic molar ratio of Mg, Li, and Ca to Al in the oxide formed on the surface of the aluminum alloy brazing sheet before brazing heating is 0.50 or less. The present invention provides an aluminum alloy brazing sheet having excellent brazability in brazing in an inert gas atmosphere without using a flux, and a method for manufacturing the same.

TECHNICAL FIELD

The present invention relates to an aluminum alloy brazing sheet usedfor brazing of aluminum or an aluminum alloy in an inert gas atmospherewithout using a flux, and a method for manufacturing the same.

BACKGROUND ART

Brazing joint is widely used as a method for joining aluminum productsincluding a number of minute joining portions, such as heat exchangersand machine components formed of aluminum. To execute brazing joint foraluminum or an aluminum alloy, it is indispensable to break an oxidefilm covering the surface thereof and expose and wet the molten brazingmaterial with a base material or a similarly molten brazing material.Methods for breaking the oxide film are broadly divided into methods ofusing a flux in a nitrogen gas furnace and methods using no flux in avacuum heating furnace, and both of them have been put to practical use.

In the methods using a flux in a nitrogen gas furnace, the flux reactswith the oxide film during brazing heating, and breaks the oxide film.However, the methods have a problem of increase in cost of the flux andcost of the step of applying a flux. In addition, when the flux isnonuniformly applied, defective brazing may occur. By contrast, in themethods using no flux in a vacuum heating furnace, a brazing materialformed of an Al—Si—Mg based alloy is used, Mg in the brazing material isevaporated by heating in vacuum, and the oxide film on the surface ofthe material is broken. However, the methods have the problem thatexpensive vacuum heating facilities are required. The methods also havethe problem that high maintenance cost is required to remove adheringMg, because evaporated Mg adheres to the inside of the furnace. For thisreason, there are increasing needs for executing joint without using aflux in a nitrogen gas furnace.

To satisfy the needs as described above, for example, Patent Literature1 proposes including Mg in the brazing material to enable surface joint.In addition, Patent Literature 2 proposes including Mg in the corematerial and diffusing Mg into the brazing material during brazingheating to enable fillet formation in a simple fin/tube joint. Inaddition, Patent Literature 2 discloses that good flux-free brazabilitycan be obtained by limiting the equivalent circle diameter and thenumber of Si particles included in the brazing material and bringing thebrazing material and the brazing target material into close contact witheach other. However, it is impossible for these methods to formsufficient fillet without application of a flux in a joint having aclearance. Specifically, in these methods, the oxide film is broken intoparticles with Mg, and thereafter a new surface of the molten brazingmaterial is exposed by a difference in thermal expansion between themolten brazing material and the oxide film or external force, such as aflow of brazing filler metal, to cause wetting. For this reason, thesemethods cause formation of distorted fillet accompanied withdiscontinuance of the fillet.

In addition, Patent Literature 3 proposes that it is effective tosuppress the thickness of a MgO film existing on the oxide film beforebrazing heating. However, in Patent Literature 3 with the brazingmaterial containing Mg of 0.1 mass % or more, because an MgO based filmis partly formed during brazing heating in a practical joint andinhibits formation of fillet, discontinuance of fillet is caused. Bycontrast, Patent Literature 4 proposes a method of removing an MgO basedfilm and enabling fluxless brazing, by executing acid cleaning for abrazing material containing Mg of 0.05 mass % or more before brazingheating. However, the method is not capable of sufficiently suppressingformation of a MgO based film during brazing heating, like PatentLiterature 1.

Patent Literature 5 proposes a brazing sheet in which oxide particlescomprising an X element (X is Mg, Li, Be, Ca, Ce, La, Y, and Zr) havinga volume change ratio of 0.99 or less to the oxide film before brazingheating are formed on the surface. Although this structure has enhancedbrazability for a more practical joint having a clearance, an actualheat exchanger has a larger clearance, and the brazability of thestructure may be insufficient.

PRIOR ART LITERATURES Patent Literatures

Patent Literature 1: Japanese Patent Application Laid-open No.2013-215797-A

Patent Literature 2: Japanese Patent No. 4547032

Patent Literature 3: Japanese Patent Application Laid-open No.2004-358519-A

Patent Literature 4: Japanese Patent Application Laid-open No.H11-285817-A

Patent Literature 5: Japanese Patent Application Laid-open No.2017-074609-A

SUMMARY OF INVENTION Problem to be Solved by Invention

An object of the present invention is to provide an aluminum alloybrazing sheet having excellent brazability even in the case of having alarge clearance, as well as a close contact part between members of aheat exchanger, in brazing in an inert gas atmosphere without using aflux, and a method for manufacturing the same.

Means for Solving Problem

The problem described above is solved by the present invention describedhereinafter.

Specifically, the present invention (1) provides an aluminum alloybrazing sheet used for brazing in an inert gas atmosphere without usinga flux, the aluminum alloy brazing sheet comprising:

a brazing material cladded onto at least one side surface of a corematerial,

the core material being formed of aluminum or an aluminum alloy corematerial comprising any one or two or more of Fe of 1.50 mass % or less,Si of 1.50 mass % or less, Cu of 2.00 mass % or less, Mn of 2.00 mass %or less, Zn of 3.00 mass % or less, Cr of 0.30 mass % or less, Ti of0.30 mass % or less, Zr of 0.30 mass % or less, In of 0.10 mass % orless, and Sn of 0.10 mass % or less, with the balance being aluminum andinevitable impurities,

the brazing material being an aluminum alloy brazing material comprisingSi of 4.00 to 13.00 mass %, and any one or two or more of Mg more than0.03 mass % and 3.00 mass % or less, Li more than 0.03 mass % and 3.00mass % or less, and Ca more than 0.03 mass % and 3.00 mass % or less,with the balance being aluminum and inevitable impurities, in which

an oxide is formed on a surface of the aluminum alloy brazing sheet bybrazing heating, the oxide including any one or two or more of Mg, Li,and Ca and having a volume change ratio of 0.990 or less to a surfaceoxide film formed before brazing heating, and

an atomic molar ratio of Mg, Li, and Ca to Al in the oxide formed on thesurface of the aluminum alloy brazing sheet before brazing heating is0.5 or less.

The present invention (2) provides the aluminum alloy brazing sheetaccording to (1), in which the aluminum alloy brazing sheet is atwo-layer material in which the brazing material is cladded onto oneside surface of the core material.

The present invention (3) provides the aluminum alloy brazing sheetaccording to (1), in which the aluminum alloy brazing sheet is athree-layer material in which the brazing material is cladded onto eachof both side surfaces of the core material.

The present invention (4) provides the aluminum alloy brazing sheetaccording to (1), in which

the aluminum alloy brazing sheet is a three-layer material in which thebrazing material is cladded onto one side surface of the core materialand a cladding material is cladded onto the other side surface of thecore material, and

the cladding material is an aluminum alloy cladding material formed ofaluminum or an aluminum alloy comprising Zn of 6.00 mass % or less, withthe balance being aluminum and inevitable impurities.

The present invention (5) provides the aluminum alloy brazing sheetaccording to any one of (1) to (4), in which the core material furthercomprises any one or two or more of Mg of 3.00 mass % or less, Li of3.00 mass % or less, and Ca of 3.00 mass % or less.

The present invention (6) provides the aluminum alloy brazing sheetaccording to any one of (1) to (6), in which the core material furthercomprises Bi of 1.00 mass % or less.

The present invention (7) provides the aluminum alloy brazing sheetaccording to any one of (1) to (6), in which the brazing materialfurther comprises Bi of 1.00 mass % or less.

The present invention (8) provides the aluminum alloy brazing sheetaccording to any one of (1) to (7), in which the brazing materialfurther comprises any one or two or more of Na of 0.05 mass % or less,Sr of 0.05 mass % or less, Sb of 0.05 mass % or less, Zn of 8.00 mass %or less, Cu of 4.00 mass % or less, Fe of 1.00 mass % or less, Mn of1.00 mass % or less, Cr of 0.30 mass % or less, Ti of 0.30 mass % orless, Zr of 0.30 mass % or less, In of 0.10 mass % or less, and Sn of0.10 mass % or less.

The present invention (9) provides the aluminum alloy brazing sheetaccording to any one of (4) to (8), in which the cladding materialfurther comprises any one or two or more of Mn of 2.00 mass % or less,Mg of 3.00 mass % or less, Si of 5.00 mass % or less, Fe of 1.50 mass %or less, Cu of 1.00 mass % or less, Ti of 0.30 mass % or less, Zr of0.30 mass % or less, Cr of 0.30 mass % or less, In of 0.10 mass % orless, and Sn of 0.10 mass % or less.

The present invention (10) provides the aluminum alloy brazing sheetaccording to any one of (1) to (9), in which the oxide formed on abrazing material surface of the aluminum alloy brazing sheet has athickness of 50 nm or less.

The present invention (11) provides a method for manufacturing analuminum alloy brazing sheet, the method comprising executing at leasthot working and cold working for (1) a stacked structure acquired bystacking a brazing material ingot and a core material ingot in thisorder; (2) a stacked structure acquired by stacking a brazing materialingot, a core material ingot, and a brazing material ingot in thisorder; or (3) a stacked structure acquired by stacking a brazingmaterial ingot, a core material ingot, and a cladding material ingot inthis order, to acquire an aluminum alloy brazing sheet, in which

the core material ingot is formed of aluminum or an aluminum alloycomprising any one or two or more of Fe of 1.50 mass % or less, Si of1.50 mass % or less, Cu of 2.00 mass % or less, Mn of 2.00 mass % orless, Zn of 3.00 mass % or less, Cr of 0.30 mass % or less, Ti of 0.30mass % or less, Zr of 0.30 mass % or less, In of 0.10 mass % or less,and Sn of 0.10 mass % or less, with the balance being aluminum andinevitable impurities,

the brazing material ingot is formed of an aluminum alloy comprising Siof 4.00 to 13.00 mass %, and any one or two or more of Mg more than 0.03mass % and 3.00 mass % or less, Li more than 0.03 mass % and 3.00 mass %or less, and Ca more than 0.03 mass % and 3.00 mass % or less, with thebalance being aluminum and inevitable impurities,

the cladding material ingot is formed of aluminum or an aluminum alloycomprising Zn of 6.00 mass % or less, with the balance being aluminumand inevitable impurities, and

intermediate annealing, final annealing, or annealing is executed, theintermediate annealing being executed between rolling passes in the coldworking to heat the stacked structure at 250 to 450° C. for one hour ormore in an atmosphere controlled to have an oxygen concentration of10,000 ppm or less and a dew point of 20° C. or less, the finalannealing being executed after a last pass of the cold working to heatthe stacked structure at 250 to 450° C. for one hour or more in anatmosphere controlled to have an oxygen concentration of 10,000 ppm orless and a dew point of 20° C. or less, and the annealing being executedboth between rolling passes in the cold working and after the last passof the cold working to heat the stacked structure at 250 to 450° C. forone hour or more in an atmosphere controlled to have an oxygenconcentration of 10,000 ppm or less and a dew point of 20° C. or less.

The present invention (12) provides the method for manufacturing analuminum alloy brazing sheet according to (11), in which the corematerial ingot further comprises any one or two or more of Mg of 3.00mass % or less, Li of 3.00 mass % or less, and Ca of 3.00 mass % orless.

The present invention (13) provides the method for manufacturing analuminum alloy brazing sheet according to (11) or (12), in which one ofthe core material ingot and the brazing material ingot further comprisesBi of 1.00 mass % or less.

The present invention (14) provides the method for manufacturing analuminum alloy brazing sheet according to any one of (11) to (13), inwhich the brazing material ingot further comprises any one or two ormore of Na of 0.05 mass % or less, Sr of 0.05 mass % or less, Sb of 0.05mass % or less, Zn of 8.00 mass % or less, Cu of 4.00 mass % or less, Feof 1.00 mass % or less, Mn of 1.00 mass % or less, Cr of 0.30 mass % orless, Ti of 0.30 mass % or less, Zr of 0.30 mass % or less, In of 0.10mass % or less, and Sn of 0.10 mass % or less.

The present invention (15) provides the method for manufacturing analuminum alloy brazing sheet according to any one of (11) to (14), inwhich the cladding material ingot further comprises any one or two ormore of Mn of 2.00 mass % or less, Mg of 3.00 mass % or less, Si of 5.00mass % or less, Fe of 1.50 mass % or less, Cu of 1.00 mass % or less, Tiof 0.30 mass % or less, Zr of 0.30 mass % or less, Cr of 0.30 mass % orless, In of 0.10 mass % or less, and Sn of 0.10 mass % or less.

The present invention (16) provides the method for manufacturing analuminum alloy brazing sheet according to any one of (11) to (15), inwhich a brazing material surface of a clad material is subjected toetching using one or both of an acid aqueous solution and an alkalineaqueous solution, the etching being executed after the intermediateannealing when the intermediate annealing is executed, after the finalannealing when the final annealing is executed, and one or both oftiming after the intermediate annealing and timing after the finalannealing when both the intermediate annealing and the final annealingare executed.

Effects of Invention

The present invention provides an aluminum alloy brazing sheet havingexcellent brazability in brazing in an inert gas atmosphere withoutusing a flux, and a method for manufacturing the same.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a diagram illustrating assembly of a clearance filling testpiece in examples and comparative examples.

EMBODIMENTS OF INVENTION

Mg, Li, and Ca break a film-like oxide formed on a surface of a brazingmaterial during brazing heating, and effectively expose a new surface ofthe molten brazing material. In addition, because Mg, Li, and Ca haveoxide generation energy smaller than that of Al, Mg, Li, and Ca reducethe film-like oxide mainly comprising Al during brazing heating, andform a particulate oxide including Mg, Li, and Ca. In particular,because the brazing material of the brazing sheet comprises any one ortwo or more of Mg, Li, and Ca more than 0.03 mass %, Mg, Li, and Ca aresufficiently diffused into the surface layer of the counterpart material(for example, a 3003 material) to which the brazing sheet is joined, andoxide particles comprising any one or two or more of Mg, Li, and Ca areformed in the 3003 material serving as the counterpart material. Thiscauses change in the volume of the oxide on the surface of thecounterpart material, and good brazability is acquired even in a jointhaving a large clearance.

An aluminum alloy brazing sheet according to the present invention is analuminum alloy brazing sheet used for brazing in an inert gas atmospherewithout using a flux, the aluminum alloy brazing sheet comprising:

a brazing material cladded onto at least one side surface of a corematerial,

the core material being formed of aluminum or an aluminum alloy corematerial comprising any one or two or more of Fe of 1.50 mass % or less,Si of 1.50 mass % or less, Cu of 2.00 mass % or less, Mn of 2.00 mass %or less, Zn of 3.00 mass % or less, Cr of 0.30 mass % or less, Ti of0.30 mass % or less, Zr of 0.30 mass % or less, In of 0.10 mass % orless, and Sn of 0.10 mass % or less, with the balance being aluminum andinevitable impurities,

the brazing material being an aluminum alloy brazing material comprisingany one or two or more of Si of 4.00 to 13.00 mass %, Mg more than 0.03mass % and 3.00 mass % or less, Li more than 0.03 mass % and 3.00 mass %or less, and Ca more than 0.03 mass % and 3.00 mass % or less, with thebalance being aluminum and inevitable impurities, in which

an oxide is formed on a surface of the aluminum alloy brazing sheet bybrazing heating, the oxide including any one or two or more of Mg, Li,and Ca and having a volume change ratio of 0.990 or less to a surfaceoxide film formed before brazing heating, and

an atomic molar ratio of Mg, Li, and Ca to Al in the oxide formed on thesurface of the aluminum alloy brazing sheet before brazing heating is0.5 or less.

The aluminum alloy brazing sheet according to the present invention isan aluminum alloy brazing sheet used for brazing in an inert gasatmosphere without using a flux. The aluminum alloy brazing sheetaccording to the present invention is a clad material in which a brazingmaterial having chemical composition illustrated as follows is claddedonto at least one side surface of a core material having chemicalcomposition illustrated as follows. The aluminum alloy brazing sheetaccording to the present invention is: (1) a two-layer material in whicha brazing material is cladded onto one side surface of a core material;(2) a three-layer material in which a brazing material is cladded ontoeach of side surfaces of a core material; or (3) a three-layer materialin which a brazing material is cladded onto one side surface of a corematerial and a cladding material is cladded onto the other side surfaceof the core material.

The core material of the aluminum alloy brazing sheet according to thepresent invention is formed of aluminum or an aluminum alloy corematerial comprising any one or two or more of Fe of 1.50 mass % or less,Si of 1.50 mass % or less, Cu of 2.00 mass % or less, Mn of 2.00 mass %or less, Zn of 3.00 mass % or less, Cr of 0.30 mass % or less, Ti of0.30 mass % or less, Zr of 0.30 mass % or less, In of 0.10 mass % orless, and Sn of 0.10 mass % or less, with the balance being aluminum andinevitable impurities.

When the core material is formed of aluminum, purity of the aluminum isnot particularly limited, but preferably is 99.0 mass % or more, andparticularly preferably 99.5 mass % or more.

In the aluminum alloy forming the core material, Fe contributes toimprovement in strength. When the core material comprises Fe, the Fecontent in the core material is 1.50 mass % or less, preferably 0.10 to0.70 mass %, and particularly preferably 0.20 to 0.60 mass %. With theFe content in the core material falling within the range describedabove, the strength of the core material increases. On the other hand,when the Fe content in the core material exceeds the range describedabove, corrosion resistance thereof decreases, and giant compounds areeasily generated.

In the aluminum alloy forming the core material, Si contributes toimprovement in strength. When the core material comprises Si, the Sicontent in the core material is 1.50 mass % or less, preferably 0.10 to1.00 mass %, and particularly preferably 0.30 to 0.75 mass %. With theSi content in the core material falling within the range describedabove, the strength of the core material increases. On the other hand,when the Si content in the core material exceeds the range describedabove, the melting point thereof becomes too low, local melting occursin brazing, and the core material is deformed to cause decrease incorrosion resistance.

In the aluminum alloy forming the core material, Cu contributes toimprovement in strength and potential adjustment. When the core materialcomprises Cu, the Cu content in the core material is 2.00 mass % orless, preferably 0.10 to 1.00 mass %, and particularly preferably 0.15to 0.80 mass %. With the Cu content in the core material falling withinthe range described above, the strength of the core material increases.On the other hand, when the Cu content in the core material exceeds therange described above, boundary corrosion easily occurs, and the meltingpoint thereof becomes too low.

In the aluminum alloy forming the core material, Mn contributes toimprovement in strength and potential adjustment. When the core materialcomprises Mn, the Mn content in the core material is 2.00 mass % orless, preferably 0.30 to 1.80 mass %, and particularly preferably 0.30to 1.50 mass %. With the Mn content in the core material falling withinthe range described above, the strength of the core material increases,and the potential adjustment effect is acquired. On the other hand, whenthe Mn content in the core material exceeds the range described above,cracks easily occur in rolling of the material.

In the aluminum alloy forming the core material, Zn contributes topotential adjustment. When the core material comprises Zn, the Zncontent in the core material is 3.00 mass % or less, preferably 0.50 to3.00 mass %, and particularly preferably 1.50 to 3.00 mass %. With theZn content in the core material falling within the range describedabove, the potential adjustment effect is acquired. On the other hand,when the Zn content in the core material exceeds the range describedabove, the natural electrode potential thereof becomes too low, and thecorrosion resistance thereof decreases.

In the aluminum alloy forming the core material, Cr improves strength bysolid solution strengthening, and precipitates Al—Cr based minutecompounds to act on grain coarsening after brazing. The Cr content inthe core material is 0.30 mass % or less, and preferably 0.10 to 0.20mass %. With the Cr content in the core material falling within therange described above, the strength of the core material is enhanced. Onthe other hand, when the Cr content in the core material exceeds therange described above, giant intermetallic compounds are easily formedin casting, and plastic workability is reduced.

In the aluminum alloy forming the core material, Ti improves strength bysolid solution strengthening, and is distributed in stratum to form ahigh potential layer and a low potential layer in the core material.With this structure, the corrosion form changes from a pitting form to astratified form, and the effect of improving corrosion resistance isexhibited. The Ti content in the core material is 0.30 mass % or less,preferably 0.10 to 0.20 mass %, and particularly preferably 0.12 to 0.18mass %. With the Ti content in the core material falling within therange described above, the strength of the core material is enhanced,and corrosion resistance thereof is enhanced. On the other hand, whenthe Ti content in the core material exceeds the range described above,giant intermetallic compounds are easily formed in casting, and plasticworkability is reduced.

In the aluminum alloy forming the core material, Zr improves strength bysolid solution strengthening, and precipitates Al—Zr based minutecompounds to act on grain coarsening after brazing. The Zr content inthe core material is 0.30 mass % or less, and preferably 0.10 to 0.20mass %. With the Zr content in the core material falling within therange described above, the strength of the core material is enhanced,and the grain coarsening effect after brazing is acquired. On the otherhand, when the Zr content in the core material exceeds the rangedescribed above, giant intermetallic compounds are easily formed incasting, and plastic workability is reduced.

In the aluminum alloy forming the core material, In contributes topotential adjustment. When the core material comprises In, the Incontent in the core material is 0.10 mass % or less, and preferably 0.01to 0.03 mass %. With the In content in the core material falling withinthe range described above, the potential adjustment effect is acquired.On the other hand, when the In content in the core material exceeds therange described above, the natural electrode potential thereof becomestoo low, and the corrosion resistance thereof decreases.

In the aluminum alloy forming the core material, Sn contributes topotential adjustment. When the core material comprises Sn, the Sncontent in the core material is 0.10 mass % or less, and preferably 0.01to 0.10 mass %. With the Sn content in the core material falling withinthe range described above, the potential adjustment effect is acquired.On the other hand, when the Sn content in the core material exceeds therange described above, the natural electrode potential thereof becomestoo low, and the corrosion resistance thereof decreases.

The core material may comprise Bi. In the aluminum alloy forming thecore material, Bi acts to suppress decrease in the Bi concentration ofthe brazing material when the brazing material is molten, and melt someof the core material during brazing heating, and exhibits the effect ofreducing the surface tension of the Al—Si molten brazing filler metal.When the core material comprises Bi, the Bi content in the core materialis 1.00 mass % or less, and preferably 0.10 to 1.00 mass %. The Bicontent in the core material falling within the range described aboveproduces the effect of being molten into the brazing material andreducing the surface tension. On the other hand, when the Bi content inthe core material exceeds the range described above, rolling of thematerial becomes difficult.

The core material may comprise any one or two or more of Mg, Li, and Ca.When the core material comprises Mg, the Mg content in the core materialis 3.00 mass % or less, and preferably 0.10 to 1.80 mass %. When thecore material comprises Li, the Li content in the core material is 3.00mass % or less, and preferably 0.10 to 1.80 mass %. When the corematerial comprises Ca, the Ca content in the core material is 3.00 mass% or less, and preferably 0.10 to 1.80 mass %. With the Mg, Li, or Cacontent in the core material falling within the range described above,Mg, Li, or Ca acts to suppress decrease in the Mg, Li, or Caconcentration of the brazing material when the brazing material ismolten, and melt some of the core material during brazing heating.Accordingly, the volume change ratio of an oxide formed by oxidizationof Mg, Li, or Ca on the surface of the brazing material becomes 0.990 orless, and the oxide film breaking effect of the brazing sheet or thecounterpart material with Mg, Li, and Ca is enhanced, and excellentbrazability is acquired. On the other hand, when the Mg, Li, or Cacontent in the core material exceeds the range described above, themelting point of the core material decreases too much, and local meltingoccurs in the core material in brazing heating. This causes deformationof the core material, causes erosion of the core material with themolten brazing filler metal, and decreases the brazing joint propertyand/or corrosion resistance.

The core material may comprise Ag, B, Be, Cd, Co, Ga, Ge, Mo, Na, Ni, P,Pb, Sr, V, Hg, and Y of 0.05 mass % or less, as inevitable impurities.

The brazing material of the aluminum alloy brazing sheet according tothe present invention is an aluminum alloy brazing material comprising:

(i) Si of 4.0 to 13.0 mass %; and

(ii) any one or two or more of Mg more than 0.03 mass % and 3.00 mass %or less, Li more than 0.03 mass % and 3.00 mass % or less, and Ca morethan 0.03 mass % and 3.00 mass % or less, with the balance beingaluminum and inevitable impurities.

The brazing material comprises Si as an indispensable element. The Sicontent in the brazing material is 4.00 to 13.00 mass %, andparticularly preferably 4.50 to 12.00 mass %. With the Si content in thebrazing material falling within the range described above, a sufficientliquid phase necessary for brazing joint is acquired. On the other hand,when the Si content in the brazing material is less than the rangedescribed above, the liquid phase quantity is insufficient. The Sicontent exceeding the range described above causes easy occurrence ofcracks in manufacturing of the material, and causes difficulty inmanufacturing of the brazing sheet.

The brazing material comprises any one or two or more of Mg, Li, and Ca.

When the brazing material comprises Mg, the Mg content in the brazingmaterial exceeds 0.03 mass % and is 3.00 mass % or less, preferably 0.10to 1.80 mass %, and particularly preferably 0.60 to 1.20 mass %. Whenthe brazing material comprises Li, the Li content in the brazingmaterial exceeds 0.03 mass % and is 3.00 mass % or less, preferably 0.04to 1.80 mass %, and particularly preferably 0.10 to 1.80 mass %. Whenthe brazing material comprises Ca, the Ca content in the brazingmaterial exceeds 0.03 mass % and is 3.00 mass % or less, preferably 0.05to 1.80 mass %, and particularly preferably 0.10 to 1.80 mass %. Withthe Mg, Li, or Ca content in the brazing material falling within therange described above, the volume change ratio of an oxide formed byoxidization of Mg, Li, or Ca during brazing heating is set to 0.990 orless to enhance the effect of breaking the oxide film on the brazingsheet or the counterpart material with Mg, Li, and Ca, and excellentbrazability is achieved. On the other hand, the Mg, Li, and Ca contentsin the brazing material less than the range described above reduce theeffect of breaking the oxide film on the brazing sheet or thecounterpart material with Mg, Li, and Ca. When the Mg, Li, and Cacontents exceed the range described above, oxidization of Mg, Li, and Caproceeds during brazing heating, and an oxide having a volume changeratio more than 0.990 is formed.

The brazing material may comprise Bi. In the aluminum alloy forming thebrazing material, Bi exhibits the effect of reducing the surface tensionof the Al—Si molten brazing filler metal. When the brazing materialcomprises Bi, the Bi content in the brazing material is 1.00 mass % orless, preferably 0.50 mass % or less, more preferably 0.05 to 0.40 mass%, and particularly preferably 0.10 to 0.30 mass %. The Bi content inthe brazing material falling within the range described above enablesthe effect of reducing the surface tension to be achieved easily. On theother hand, when the Bi content in the brazing material exceeds therange described above, the surface of the brazing material after brazingis discolored into black, and the brazability is reduced.

The brazing material may comprise any one or two or more of Na, Sr, andSb. In the aluminum alloy forming the brazing material, Na, Sr, and Sbmicronize the Si particles in the brazing material, and exhibit theeffect of enhancing flowability of the brazing filler metal. When thebrazing material comprises Na, the Na content in the brazing material is0.05 mass % or less, preferably 0.005 to 0.04 mass %, and particularlypreferably 0.007 to 0.04 mass %. When the brazing material comprises Sr,the Sr content in the brazing material is 0.05 mass % or less,preferably 0.005 to 0.04 mass %, and particularly preferably 0.005 to0.02 mass %. When the brazing material comprises Sb, the Sb content inthe brazing material is 0.05 mass % or less, and preferably 0.005 to0.04 mass %.

The brazing material may comprise any one or two of Zn and Cu. In thealuminum alloy forming the brazing material, Zn and Cu reduce themelting point of the brazing material, and enable brazing at atemperature lower than 600° C. serving as an ordinary brazingtemperature. When the brazing material comprises Zn, the Zn content inthe brazing material is preferably 8.00 mass % or less, more preferably1.00 to 8.00 mass %, particularly preferably 2.00 to 8.00 mass %, andfurther preferably 3.00 to 5.00 mass %, from the viewpoint of easilyachieving the effect of reducing the melting point of the brazingmaterial. On the other hand, when the Zn content in the brazing materialexceeds 8.00 mass %, cracks occur in the brazing material during coldrolling, and no sound sheet material is acquired. In addition, when thebrazing material comprises Zn, the Zn content in the brazing material ispreferably 3.00 mass % or less, from the viewpoint of easily acquiringthe effect of preventing the core material from being corroded bysetting the potential of the brazing material less-noble and corrodingthe brazing material with priority over the core material. When thebrazing material comprises Cu, the Cu content in the brazing material is4.00 mass % or less, preferably 0.50 to 4.00 mass %, and particularlypreferably 1.00 to 2.50 mass %. The Cu content in the brazing materialfalling within the range described above enhances the effect of reducingthe melting point of the brazing material. On the other hand, when theCu content in the brazing material exceeds the range described above,cracks occur in the brazing material during cold rolling, and no soundsheet material is acquired.

The brazing material may comprise Fe. In the aluminum alloy forming thebrazing material, Fe crystallizes Al—Fe based relatively coarsecompounds to act on grain micronizing of the brazing material afterbrazing. When the brazing material comprises Fe, the Fe content in thebrazing material is 1.00 mass % or less, preferably 0.10 to 0.50 mass %,and particularly preferably 0.20 to 0.50 mass %. With the Fe content inthe brazing material falling within the range described above, the grainmicronizing effect is easily acquired. On the other hand, when the Fecontent in the brazing material exceeds the range described above, giantintermetallic compounds are easily formed in casting, and plasticworkability is reduced.

The brazing material may comprise any one or two or more of Mn, Cr, Ti,and Zr. In the aluminum alloy forming the brazing material, Mn, Cr, Ti,and Zr precipitate Al—Mn based, Al—Cr based, Al—Ti based, and Al—Zrbased relatively coarse compounds, respectively, to act on graincoarsening after brazing. When the brazing material comprises Mn, the Mncontent in the brazing material is 1.00 mass % or less, and preferably0.10 to 0.60 mass %. With the Mn content in the brazing material fallingwithin the range described above, the grain coarsening effect is easilyacquired. On the other hand, when the Mn content in the brazing materialexceeds the range described above, giant intermetallic compounds areeasily formed in casting, and plastic workability is reduced. When thebrazing material comprises Cr, the Cr content in the brazing material is0.30 mass % or less, and preferably 0.01 to 0.03 mass %. With the Crcontent in the brazing material falling within the range describedabove, the grain coarsening effect is easily acquired. On the otherhand, when the Cr content in the brazing material exceeds the rangedescribed above, giant intermetallic compounds are easily formed incasting, and plastic workability is reduced. When the brazing materialcomprises Ti, the Ti content in the brazing material is 0.30 mass % orless, preferably 0.10 mass % or less, and particularly preferably 0.01to 0.03 mass %. With the Ti content in the brazing material fallingwithin the range described above, the grain coarsening effect is easilyacquired. On the other hand, when the Ti content in the brazing materialexceeds the range described above, giant intermetallic compounds areeasily formed in casting, and plastic workability is reduced. When thebrazing material comprises Zr, the Zr content in the brazing material is0.30 mass % or less, and preferably 0.01 to 0.03 mass %. With the Zrcontent in the brazing material falling within the range describedabove, the grain coarsening effect is easily acquired. On the otherhand, when the Zr content in the brazing material exceeds the rangedescribed above, giant intermetallic compounds are easily formed incasting, and plastic workability is reduced. The grain size afterbrazing is adjusted using the actions described above. The effect of thepresent invention can be sufficiently acquired within the rangedescribed above.

The brazing material may comprise In. In the aluminum alloy forming thebrazing material, In exhibits the effect of preventing the core materialfrom being corroded by setting the potential of the brazing materialless-noble and corroding the brazing material with priority over thecore material. When the brazing material comprises In, the In content inthe brazing material is 0.10 mass % or less, preferably 0.01 to 0.03mass %, and particularly preferably 0.02 to 0.03 mass %. With the Incontent in the brazing material falling within the range describedabove, the potential adjustment effect is easily acquired. On the otherhand, when the In content in the brazing material exceeds the rangedescribed above, the natural electrode potential becomes too low, andthe corrosion resistance is reduced.

The brazing material may comprise Sn. In the aluminum alloy forming thebrazing material, Sn exhibits the effect of preventing the core materialfrom being corroded by setting the potential of the brazing materialless-noble and corroding the brazing material with priority over thecore material. When the brazing material comprises Sn, the Sn content inthe brazing material is 0.10 mass % or less, and preferably 0.01 to 0.05mass %. With the Sn content in the brazing material falling within therange described above, the potential adjustment effect is easilyacquired. On the other hand, when the Sn content in the brazing materialexceeds the range described above, the natural electrode potentialbecomes too low, and the corrosion resistance is reduced.

The brazing material may comprise Ag, B, Be, Cd, Co, Ga, Ge, Mo, Ni, P,Pb, V, Hg, and Y of 0.05 mass % or less, as inevitable impurities.

The cladding material of the aluminum alloy brazing sheet according tothe present invention is formed of aluminum or an aluminum alloycladding material comprising Zn of 6.00 mass % or less, with the balancebeing aluminum and inevitable impurities. In the aluminum alloy brazingsheet according to the present invention, because the cladding materialis cladded, the corrosion resistance of the aluminum product afterbrazing is further improved by the sacrificial anticorrosive effect. Inthe aluminum alloy brazing sheet according to the present invention, anoxide is formed on a surface on the brazing material side during brazingheating, and the oxide includes any one or two or more of Mg, Li, and Caand has a volume change ratio of 0.990 or less, preferably 0.700 to0.970, more preferably 0.700 to 0.950, and particularly preferably 0.800to 0.900, to a surface oxide film formed before brazing heating. Withthis structure, a new surface of the brazing material is exposed inbrazing heating in an inert gas atmosphere without using a flux, and thealuminum alloy brazing sheet has excellent brazability. For this reason,the aluminum alloy brazing sheet according to the present inventionproduces the effect of the present invention described above, regardlessof whether the cladding material is cladded, or not cladded, onto asurface of the core material opposite to a surface provided with thebrazing material.

When the cladding material is formed of aluminum, the purity of thealuminum is not particularly limited, but preferably 99.0 mass % ormore, and particularly preferably 99.5 mass % or more.

When the cladding material is formed of an aluminum alloy comprising Zn,the Zn content in the cladding material is 6.00 mass % or less, andpreferably 3.00 mass % or less. With the Zn content in the claddingmaterial falling within the range described above, the sacrificialanticorrosive effect is enhanced. On the other hand, when the Zn contentin the cladding material exceeds the range described above, thepotential of the cladding material excessively decreases, and theprogress of corrosion may be enhanced.

The cladding material may comprise Mn. In the aluminum alloy forming thecladding material, Mn contributes to improvement in strength. When thecladding material comprises Mn, the Mn content in the cladding materialis 2.00 mass % or less, and preferably 0.30 to 1.80 mass %. With the Mncontent in the cladding material falling within the range describedabove, the strength improvement effect is easily acquired. On the otherhand, when the Mn content in the cladding material exceeds the rangedescribed above, cracks easily occur in rolling of the material.

The cladding material may comprise Mg. In the aluminum alloy forming thecladding material, Mg contributes to improvement in strength. When thecladding material comprises Mg, the Mg content in the cladding materialis 3.00 mass % or less, preferably 0.30 to 1.80 mass %, and particularlypreferably 0.40 to 1.80 mass %. With the Mg content in the claddingmaterial falling within the range described above, the strengthimprovement effect is easily acquired. On the other hand, when the Mgcontent in the cladding material exceeds the range described above,cracks easily occur in rolling of the material.

The cladding material may comprise Si. In the aluminum alloy forming thecladding material, Si contributes to improvement in strength. When thecladding material comprises Si, the Si content in the cladding materialis 5.00 mass % or less, preferably 0.10 to 1.50 mass %, more preferably0.10 to 1.00 mass %, and particularly preferably 0.20 to 1.00 mass %.With the Si content in the cladding material falling within the rangedescribed above, the strength of the cladding material increases. Inaddition, the Si content in the cladding material is 1.50 to 5.00 mass%, and particularly preferably 2.50 to 4.50 mass %. When the Si contentfalls within the range of 1.50 to 5.00 mass %, the cladding materialchanges to a semi-molten state during brazing heating to supply a verysmall quantity of liquid-phase brazing filler metal and enhancebrazability when the cladding material surface serves as the brazingsurface. When the Si content in the cladding material exceeds the rangedescribed above, the melting point becomes too low, melting occurs inbrazing, and the cladding material is deformed.

The cladding material may comprise Fe. In the aluminum alloy forming thecladding material, Fe contributes to improvement in strength. When thecladding material comprises Fe, the Fe content in the cladding materialis 1.50 mass % or less, preferably 0.10 to 0.70 mass %, and particularlypreferably 0.10 to 0.50 mass %. With the Fe content in the claddingmaterial falling within the range described above, the strengthimprovement effect is easily acquired. On the other hand, when the Fecontent in the cladding material exceeds the range described above, thecorrosion resistance decreases, and giant compounds are easilygenerated.

The cladding material may comprise Cu. In the aluminum alloy forming thecladding material, Cu contributes to improvement in strength. When thecladding material comprises Cu, the Cu content in the cladding materialis 1.00 mass % or less, and preferably 0.10 to 1.00 mass %. With the Cucontent in the cladding material falling within the range describedabove, the strength improvement effect is easily acquired. On the otherhand, when the Cu content in the cladding material exceeds the rangedescribed above, boundary corrosion easily occurs.

The cladding material may comprise any one or two or more of Ti, Zr, andCr. In the aluminum alloy forming the cladding material, Ti, Zr, and Crexhibit the effect of improving strength by solid solutionstrengthening. When the cladding material comprises Ti, the Ti contentin the cladding material is 0.30 mass % or less, and preferably 0.10 to0.20 mass %. When the cladding material comprises Zr, the Zr content inthe cladding material is 0.30 mass % or less, and preferably 0.10 to0.20 mass %. When the cladding material comprises Cr, the Cr content inthe cladding material is 0.30 mass % or less, and preferably 0.10 to0.20 mass %. With the Ti, Zr, or Cr content in the cladding materialfalling within the range described above, the strength improvementeffect is easily acquired. On the other hand, when the Ti, Zr, or Crcontent in the cladding material exceeds the range described above,giant intermetallic compounds are easily formed in casting, and plasticworkability is reduced.

The cladding material may comprise In. In the aluminum alloy forming thecladding material, In exhibits the effect of preventing the corematerial from being corroded by setting the potential of the claddingmaterial less-noble and corroding the cladding material with priorityover the core material. When the cladding material comprises In, the Incontent in the cladding material is 0.10 mass % or less, and preferably0.01 to 0.03 mass %. With the In content in the cladding materialfalling within the range described above, the potential adjustmenteffect is easily acquired. On the other hand, when the In content in thecladding material exceeds the range described above, the naturalelectrode potential becomes too low, and the corrosion resistance isreduced.

The cladding material may comprise Sn. In the aluminum alloy forming thecladding material, Sn exhibits the effect of preventing the corematerial from being corroded by setting the potential of the claddingmaterial less-noble and corroding the cladding material with priorityover the core material. When the cladding material comprises Sn, the Sncontent in the cladding material is 0.10 mass % or less, and preferably0.01 to 0.05 mass %. With the Sn content in the cladding materialfalling within the range described above, the potential adjustmenteffect is easily acquired. On the other hand, when the Sn content in thecladding material exceeds the range described above, the naturalelectrode potential becomes too low, and the corrosion resistance isreduced.

The cladding material may comprise Ag, B, Be, Bi, Ca, Cd, Co, Ga, Ge,Li, Mo, Na, Ni, P, Pb, Sr, V, and Hg of 0.05 mass % or less, asinevitable impurities.

The aluminum alloy brazing sheet according to the present invention isan aluminum alloy brazing sheet in which an oxide is formed on a surfacethereof by brazing heating in an inert gas atmosphere without using aflux, and the oxide includes any one or two or more of Mg, Li, and Caand has a volume change ratio of 0.990 or less, preferably 0.700 to0.970, more preferably 0.700 to 0.950, and particularly preferably 0.800to 0.900, to a surface oxide film formed before brazing heating. Inbrazing heating in an inert gas atmosphere without using a flux, whenthe oxide including Mg, Li, and Ca and having been subjected to brazingheating has a volume change ratio falling within the range describedabove to a surface oxide formed before brazing heating, and the formedparticulate oxide includes Mg, Li, and Ca, because a new surface of thebrazing material is effectively exposed in brazing heating, the aluminumalloy brazing sheet has excellent brazability.

By contrast, in brazing heating in an inert gas atmosphere without usinga flux, when the oxide including one or two or more of Mg, Li, and Caand having been subjected to brazing heating has a volume change ratioexceeding the range described above to a surface oxide formed beforebrazing heating, a new surface of the brazing material is not easilyexposed in brazing heating. In the present invention, the volume changeratio of the oxide including one or two or more of Mg, Li, and Ca andformed by brazing heating is a volume change ratio to an oxide filmformed on a surface of the brazing surface before brazing, and a valuedetermined using the expression “volume per oxygen atom of oxideparticles comprising one or two or more of Mg, Li, and Ca and formed bybrazing heating/volume per oxygen atom of an oxide film formed on thesurface of the brazing material before brazing”. In the expression, thevolume per oxygen atom is calculated by dividing the molecular weight ofthe oxide by density of the oxide.

Mg, Li, and Ca have oxide generation free energy smaller than that ofAl, and are capable of not only reducing the oxide film but also formingan oxide having a volume change ratio of 0.990 or less. For this reason,Mg, Li, and Ca are content elements effective for exposing a new surfaceof the brazing material in brazing heating. For example, although avolume change ratio of MgO is 0.994, a volume change ratio of MgAl₂O₄ is0.863 and smaller than 0.990. By contrast, Ba, Th, and Nd and the likeare elements having oxide generation free energy smaller than that ofAl, but are not effective content elements because they have no oxidehaving a volume change ratio of 0.990 or less. For example, volumechange ratios of BaO and BaAl₂O₄ serving as oxides comprising Ba are2.366 and 1.377, respectively, and Ba has no oxide having a volumechange ratio of 0.990 or less.

An oxide film is formed on a surface of the brazing material of thealuminum alloy brazing sheet according to the present invention. Inaddition, a molar ratio of each of Mg, Li, and Ca to Al in the oxidefilm formed on the surface of the brazing material of the aluminum alloybrazing sheet according to the present invention is 0.50 or less interms of atom. With the molar ratio (such as Mg/Al) of each of Mg, Li,and Ca to Al in the oxide film formed on the surface of the brazingmaterial falling within the range described above in terms of atom, thevolume change ratio of the oxide including Mg, Li, and Ca and formed bybrazing heating on the oxide film formed on the surface of the brazingmaterial before brazing is set to 0.990 or less. When the oxide filmformed on the surface of the brazing material of the aluminum alloybrazing sheet according to the present invention comprises two or moreof elements of Mg, Li, and Ca, the fact that the molar ratio of each ofMg, Li, and Ca to Al is 0.50 or less in terms of atom means that themolar ratio of each of Mg, Li, and Ca to Al is 0.5 or less in terms ofatom for any of Mg, Li, and Ca.

The thickness of the oxide film formed on the surface of the brazingmaterial of the aluminum alloy brazing sheet according to the presentinvention is preferably 50 nm or less, and more preferably 10 nm orless, in terms of easiness of breakage of the oxide film. When thethickness of the oxide film formed on the surface of the brazingmaterial exceeds 50 nm, breakage of the oxide film becomes difficult toprogress.

The aluminum alloy brazing sheet according to the present invention issuitably manufactured by a method for manufacturing the aluminum alloybrazing sheet according to the present invention described hereinafter.

A method for manufacturing an aluminum alloy brazing sheet according tothe present invention is a method for manufacturing aluminum alloybrazing sheet, comprising executing at least hot working and coldworking for (1) a stacked structure acquired by stacking a brazingmaterial ingot and a core material ingot in this order; (2) a stackedstructure acquired by stacking a brazing material ingot, a core materialingot, and a brazing material ingot in this order; or (3) a stackedstructure acquired by stacking a brazing material ingot, a core materialingot, and a cladding material ingot in this order, to acquire analuminum alloy brazing sheet, in which

the core material ingot is formed of aluminum or an aluminum alloycomprising any one or two or more of Fe of 1.50 mass % or less, Si of1.50 mass % or less, Cu of 2.00 mass % or less, Mn of 2.00 mass % orless, Zn of 3.00 mass % or less, Cr of 0.30 mass % or less, Ti of 0.30mass % or less, Zr of 0.30 mass % or less, In of 0.10 mass % or less,and Sn of 0.10 mass % or less, with the balance being aluminum andinevitable impurities,

the brazing material ingot is formed of an aluminum alloy comprising Siof 4.00 to 13.00 mass %, and any one or two or more of Mg more than 0.03mass % and 3.00 mass % or less, Li more than 0.03 mass % and 3.00 mass %or less, and Ca more than 0.03 mass % and 3.00 mass % or less, with thebalance being aluminum and inevitable impurities,

the cladding material ingot is formed of aluminum or an aluminum alloycomprising Zn of 6.00 mass % or less, with the balance being aluminumand inevitable impurities, and

intermediate annealing, final annealing, or annealing is executed, theintermediate annealing being executed between rolling passes in the coldworking to heat the stacked structure at 250 to 450° C. for one hour ormore in an atmosphere controlled to have an oxygen concentration of10,000 ppm or less and a dew point of 20° C. or less, the finalannealing being executed after a last pass of the cold working to heatthe stacked structure at 250 to 450° C. for one hour or more in anatmosphere controlled to have an oxygen concentration of 10,000 ppm orless and a dew point of 20° C. or less, and the annealing being executedboth between rolling passes in the cold working and after the last passof the cold working to heat the stacked structure at 250 to 450° C. forone hour or more in an atmosphere controlled to have an oxygenconcentration of 10,000 ppm or less and a dew point of 20° C. or less.

A method for manufacturing an aluminum alloy brazing sheet according tothe present invention is a method for manufacturing an aluminum alloybrazing sheet, comprising executing at least hot working and coldworking for: (1) a stacked structure acquired by superimposing a brazingmaterial ingot and a core material ingot; (2) a stacked structureacquired by superimposing a brazing material ingot on each of both sidesurfaces of the core material ingot; or a stacked structure acquired bysuperimposing a brazing material ingot on one side surface of a corematerial ingot and superimposing a cladding material ingot on the otherside surface of the core material ingot, that is, (1) a stackedstructure acquired by stacking a brazing material ingot and a corematerial ingot in this order; (2) a stacked structure acquired bystacking a brazing material ingot, a core material ingot, and a brazingmaterial ingot in this order; or (3) a stacked structure acquired bystacking a brazing material ingot, a core material ingot, and a claddingmaterial ingot in this order, to acquire an aluminum alloy brazingsheet.

In the method for manufacturing an aluminum alloy brazing sheetaccording to the present invention, the types and the contents of theaddition compositions in the core material ingot, the brazing materialingot, and the cladding material ingots are the same as the compositionsand the contents of those in the core material, the brazing material,and the cladding material of the aluminum alloy brazing sheet accordingto the present invention.

Specifically, the core material ingot is formed of aluminum or analuminum alloy comprising any one or two or more of Fe of 1.50 mass % orless, preferably 0.10 to 0.70 mass %, and particularly preferably 0.20to 0.60 mass %, Si of 1.50 mass % or less, preferably 0.10 to 1.00 mass%, and particularly preferably 0.30 to 0.75 mass %, Cu of 2.00 mass % orless, preferably 0.10 to 1.00 mass %, and particularly preferably 0.15to 0.80 mass %, Mn of 2.00 mass % or less, preferably 0.30 to 1.80 mass%, and particularly preferably 0.30 to 1.50 mass %, Zn of 3.00 mass % orless, preferably 0.50 to 3.00 mass %, and particularly preferably 1.50to 3.00 mass %, Cr of 0.30 mass % or less, and preferably 0.10 to 0.20mass %, Ti of 0.30 mass % or less, preferably 0.10 to 0.20 mass %, andparticularly preferably 0.12 to 0.18 mass %, Zr of 0.30 mass % or less,and preferably 0.10 to 0.20 mass %, In of 0.10 mass % or less, andpreferably 0.01 to 0.03 mass %, and Sn of 0.10 mass % or less, andpreferably 0.01 to 0.10 mass %, and comprising, if necessary, Bi of 1.00mass % or less, and preferably 0.10 to 1.00 mass %, and, if necessary,any one or two or more of Mg of 3.00 mass % or less, and preferably 0.10to 1.80 mass %, Li of 3.00 mass % or less, and preferably 0.10 to 1.80mass %, and Ca of 3.00 mass % or less, and preferably 0.10 to 1.80 mass%, with the balance being aluminum and inevitable impurities. The corematerial ingot may comprise Ag, B, Be, Cd, Co, Ga, Ge, Mo, Na, Ni, P,Pb, Sr, V, Hg, and Y of 0.05 mass % or less, as inevitable impurities.

The brazing material ingot is formed of an aluminum alloy comprising Siof 4.00 to 13.00 mass %, and particularly preferably 4.50 to 12.00 mass%, and any one or two or more of Mg more than 0.03 mass % and 3.00 mass% or less, preferably 0.10 to 1.80 mass %, and particularly preferably0.60 to 1.20 mass %, Li more than 0.03 mass % and 3.00 mass % or less,preferably 0.04 to 1.80 mass %, and particularly preferably 0.10 to 1.80mass %, and Ca more than 0.03 mass % and 3.00 mass % or less, preferably0.05 to 1.80 mass %, and particularly preferably 0.10 to 1.80 mass %,and comprising, if necessary, Bi of 1.00 mass % or less, preferably 0.50mass % or less, more preferably 0.05 to 0.40 mass %, and particularlypreferably 0.10 to 0.30 mass %, and, if necessary, any one or two ormore of Na of 0.05 mass % or less, preferably 0.005 to 0.04 mass %, andparticularly preferably 0.007 to 0.04 mass %, Sr of 0.05 mass % or less,preferably 0.005 to 0.04 mass %, and particularly preferably 0.005 to0.02 mass %, Sb of 0.05 mass % or less, and preferably 0.005 to 0.04mass %, Zn of 8.00 mass % or less, preferably 1.00 to 8.00 mass %, morepreferably 2.00 to 8.00 mass %, and particularly preferably 3.00 to 5.00mass %, Cu of 4.00 mass % or less, preferably 0.50 to 4.00 mass %, andparticularly preferably 1.00 to 2.50 mass %, Fe of 1.00 mass % or less,preferably 0.10 to 0.50 mass %, and particularly preferably 0.20 to 0.50mass %, Mn of 1.00 mass % or less, and preferably 0.10 to 0.60 mass %,Cr of 0.30 mass % or less, and preferably 0.01 to 0.03 mass %, Ti of0.30 mass % or less, preferably 0.10 mass % or less, and particularlypreferably 0.01 to 0.03 mass %, Zr of 0.30 mass % or less, andpreferably 0.01 to 0.03 mass %, In of 0.10 mass % or less, preferably0.01 to 0.03 mass %, and particularly preferably 0.02 to 0.03 mass %,and Sn of 0.10 mass % or less, and preferably 0.01 to 0.05 mass %, withthe balance being aluminum and inevitable impurities. The brazingmaterial ingot may comprise one or two or more of Ag, B, Be, Cd, Co, Ga,Ge, Mo, Ni, P, Pb, V, Hg, and Y of 0.05 mass % or less, as inevitableimpurities.

The cladding material ingot is formed of aluminum or an aluminum alloycomprising Zn of 6.00 mass % or less, and preferably 3.00 mass % orless, and, if necessary, any one or two of more of Mn of 2.00 mass % orless, and preferably 0.30 to 1.80 mass %, Mg of 3.00 mass % or less,preferably 0.30 to 1.80 mass %, and particularly preferably 0.40 to 1.80mass %, Si of 5.00 mass % or less, preferably 0.10 to 1.50 mass %, morepreferably 0.10 to 1.00 mass %, and particularly preferably 0.20 to 1.00mass % or Si of 5.00 mass % or less, and preferably 2.50 to 4.50 mass %,Fe of 1.50 mass % or less, preferably 0.10 to 0.70 mass %, andparticularly preferably 0.10 to 0.50 mass %, Cu of 1.00 mass % or less,and preferably 0.10 to 1.00 mass %, Ti of 0.30 mass % or less, andpreferably 0.10 to 0.20 mass %, Zr of 0.30 mass % or less, andpreferably 0.10 to 0.20 mass %, Cr of 0.30 mass % or less, andpreferably 0.10 to 0.20 mass %, In of 0.10 mass % or less, andpreferably 0.01 to 0.03 mass %, and Sn of 0.10 mass % or less, andpreferably 0.01 to 0.05 mass %, with the balance being aluminum andinevitable impurities. The cladding material ingot may comprise Ag, B,Be, Bi, Ca, Cd, Co, Ga, Ge, Li, Mo, Na, Ni, P, Pb, Sr, V, Hg, and Y of0.05 mass % or less, as inevitable impurities.

In the method for manufacturing an aluminum alloy brazing sheetaccording to the present invention, hot rolling and cold rolling areexecuted for (1) a stacked structure acquired by stacking a brazingmaterial ingot and a core material ingot in this order; (2) a stackedstructure acquired by stacking a brazing material ingot, a core materialingot, and a brazing material ingot in this order; or (3) a stackedstructure acquired by stacking a brazing material ingot, a core materialingot, and a cladding material ingot in this order. In hot rolling, aclad sheet is formed at 400 to 550° C., and thereafter processed to havea thickness of 2 to 3 mm while kept in a hot state. In cold rolling, aclad sheet is rolled with a plurality of passes in a cold manner andprocessed to have a predetermined thickness of an aluminum alloy brazingsheet.

In the method for manufacturing an aluminum alloy brazing sheetaccording to the present invention, intermediate annealing, finalannealing, or annealing is executed. The intermediate annealing isexecuted between rolling passes in the cold working to heat the stackedstructure at 250 to 450° C. for one hour or more in an atmospherecontrolled to have an oxygen concentration of 10,000 ppm or less and adew point of 20° C. or less, the final annealing is executed after thelast pass of the cold working to heat the stacked structure at 250 to450° C. for one hour or more in an atmosphere controlled to have anoxygen concentration of 10,000 ppm or less and a dew point of 20° C. orless, and the annealing is executed both between rolling passes in thecold working and after the last pass of the cold working to heat thestacked structure at 250 to 450° C. for one hour or more in anatmosphere controlled to have an oxygen concentration of 10,000 ppm orless and a dew point of 20° C. or less. The intermediate annealing orthe final annealing has a large influence on the state of the oxidefilm, because it is a high-temperature step. The atmosphere of theintermediate annealing or the final annealing is an inert gasatmosphere, such as nitrogen gas, argon gas, and carbon dioxide gas. Byexecuting intermediate annealing or final annealing in an atmospherecontrolled to have an oxygen concentration of 10,000 ppm or less and adew point of 20° C. or less, an aluminum alloy brazing sheet is easilyacquired in which oxide particles comprising Mg, Li, and Ca and having avolume change ratio of 0.990 or less to an oxide film formed beforebrazing heating are formed on the surface thereof by brazing heating.When the oxygen concentration in the atmosphere in intermediateannealing or final annealing exceeds 10,000 ppm, growth of an oxide filmis promoted, and/or the concentration of Mg, Li, and Ca in the oxidefilm easily increases. When the dew point of the atmosphere inintermediate annealing or final annealing exceeds 20° C., a hydroxidefilm is easily formed, and the oxide film is easily thickened.

In the method for manufacturing an aluminum alloy brazing sheetaccording to the present invention, if necessary, the brazing materialsurface of the brazing sheet may be etched using an acid aqueoussolution and/or an alkaline aqueous solution, after intermediateannealing or final annealing is executed. Executing etching embrittlesor removes the oxide film formed by heating in the intermediateannealing or the final annealing. As a result, brazability of thebrazing sheet can be further improved. In the case of etching thesurface of the brazing material, when the brazing material is claddedonto one side surface of the core material, only the brazing materialsurface may be etched, or both the brazing material surface and theopposite surface may be etched. When the brazing material is claddedonto both side surfaces of the core material, both the side surfaces areetched.

Examples of the acid solution used for etching of the brazing sheetinclude aqueous solutions, such as sulfuric acid, hydrochloric acid,nitric acid, phosphoric acid, and hydrofluoric acid. One of the acidsmay be used, or two or more of the acids may be used together. From theviewpoint of more efficiently removing the oxide film, it is preferableto use a mixed aqueous solution comprising hydrofluoric acid and acidother than hydrofluoric acid as the acid, and more preferable to use amixed aqueous solution of hydrofluoric acid and sulfuric acid or a mixedaqueous solution of hydrofluoric acid and nitric acid. Examples of thealkaline solution used for etching of the brazing sheet include aqueoussolutions, such as sodium hydroxide, potassium hydroxide, and calciumhydroxide. One of the alkaline solutions may be used, or two or more ofthe alkaline solutions may be used together. In the case of executingetching using an alkaline solution, desmutting is preferably carried outusing a sulfuric acid aqueous solution and/or a nitric acid solutionafter the etching.

In the method for manufacturing an aluminum alloy brazing sheetaccording to the present invention, it is preferable to suppress growthof an oxide film and concentration of Mg, Li, and Ca into the oxide filmduring the manufacturing process.

The aluminum alloy brazing sheet according to the present invention isused for brazing in an inert gas atmosphere without using a flux. Inaddition, the aluminum alloy brazing sheet according to the presentinvention is subjected to brazing heating in an inert gas atmospherewithout using a flux. In this manner, since oxide particles comprisingMg, Li, and Ca having a volume change ratio of 0.990 or less to theoxide film formed before brazing heating are formed on the surface ofthe aluminum alloy brazing sheet, a new surface of the brazing materialis easily exposed, and excellent brazability is exhibited.

An aluminum alloy sheet (A) according to the present invention is analuminum alloy sheet acquired by subjecting the aluminum alloy brazingsheet according to the present invention to brazing heating in an inertgas atmosphere without using a flux, in which oxide particles comprisingMg, Li, and Ca and having a volume change ratio of 0.990 or less to theoxide of the aluminum alloy brazing sheet having not been subjected tobrazing heating are formed on the surface of the aluminum alloy sheet.Because the oxide of Mg, Li, and Ca formed on the surface of thealuminum alloy sheet (A) according to the present invention isparticulate and has a volume change ratio of 0.990 or less to the oxideof the aluminum alloy brazing sheet having not been subjected to brazingheating, a new surface of aluminum alloy appears in part of the surfaceof the brazing sheet in brazing heating. Examples of the inert gasinclude nitrogen gas and argon gas. During the temperature rising, theoxygen concentration in the furnace when the temperature of the brazingsheet is 400° C. or more is 100 ppm or less, and the oxygenconcentration when the temperature of the brazing sheet is 570° C. ormore is 20 ppm or less, and preferably 10 ppm or less.

The aluminum alloy sheet (A) according to the present invention is analuminum alloy sheet acquired after the aluminum alloy brazing sheet isbrazed.

EXAMPLES

The following is an explanation of examples of the present invention incomparison with comparative examples to demonstrate an effect of thepresent invention. The examples illustrate embodiments of the presentinvention, and the present invention is not limited thereto.

Core material ingots and brazing material ingots having compositionslisted in Table 1 and Table 2 were casted by continuous casting. Each ofthe acquired core material ingots was subjected to facing to a size of163 mm×163 mm. Thereafter, each of the core material ingots to becladded with a brazing material on only one side surface was subjectedto facing to a size having a thickness of 27 mm, and each of the corematerial ingots to be cladded with a brazing material on both sidesurfaces was subjected to facing to a size having a thickness of 24 mm.Each of the acquired brazing material ingots was subjected to hotrolling to a thickness of 3 mm at 500° C., and cut into sizes of 163mm×163 mm after being cooled.

TABLE 1 Material Alloy composition (mass %) number Mg Li Ca Fe Si Cu MnZn Cr Ti Zr In Bi Al C1 0.60 — — 0.60 0.30 0.15 1.20 — — — — — — BalanceC2 0.60 — — 0.20 0.50 0.50 1.20 — — — — — — Balance C3 0.50 — — 0.200.50 0.50 1.20 — — — — — — Balance C4 0.60 — — 0.20 0.30 0.15 1.20 — — —— — — Balance C5 1.00 — — 0.20 0.30 0.15 1.20 — — — — — — Balance C60.60 — — 0.20 0.30 0.15 1.20 — — 0.15 — — — Balance C7 — — — 0.20 0.300.15 1.20 — — — — — — Balance C8 — — — 0.20 0.50 0.50 1.20 — — — — — —Balance C9 1.00 — — 0.60 0.30 0.15 1.20 — — — — — — Balance C10 — — —0.60 0.25 0.15 1.15 — — — — — — Balance C11 — — — 0.20 0.30 — 1.20 1.50— — — — — Balance C12 0.60 — — 0.50 0.20 0.15 1.20 — — — — — — BalanceC13 0.35 — — 0.20 0.75 0.80 1.50 — — — — — — Balance

TABLE 2 Material Alloy composition (mass %) number Si Mg Li Ca Bi Sr ZnCu Fe Mn Cr Ti Zr In Ba Na Al F1 16.00 0.60 — — — — — — 0.20 — — — — — —— Balance F2 10.00 — — 0.05 — — — — 0.20 — — — — — — — Balance F3 12.001.00 — — 0.30 — — — 0.20 — — — — — — 0.007 Balance F4 10.00 0.10 — —0.15 0.02 — — 0.20 — — — — — — — Balance F5 10.00 0.60 — — 0.15 0.021.00 — 0.20 — — 0.10 — — — — Balance F6 12.00 0.60 — — 0.05 — — — 0.20 —— — — — — — Balance F7 12.00 0.60 — — 0.30 — — — 0.20 — — — — — — —Balance F8  4.50 0.60 — — 0.10 — 4.00 — 0.20 — — — — — — — Balance F9 7.00 0.60 — — 0.10 — 4.00 — 0.20 — — — — — — — Balance F10 12.00 0.10 —— 0.05 — — — 0.20 — — — — — — — Balance F11 10.00 0.60 — — 0.30 — — —0.20 — — 0.10 — — — — Balance F12 12.00 0.60 — — 0.30 — 2.00 — 0.20 — —— — — — — Balance F13 12.00 1.20 — — 0.30 — — — 0.20 — — — — — — —Balance F14 12.00 2.92 — — 0.30 — — — 0.20 — — — — — — — Balance F1510.00 1.20 — — 0.10 — — — 0.20 — — — — 0.02 — — Balance F16 12.00 0.60 —— 0.30 — — — 0.20 — — — — — — — Balance F17 10.00 0.60 — — — — — — 0.20— — — — — — — Balance F18 10.00 3.00 — — — — — — 0.20 — — — — — — —Balance F19 10.00 — — — — — — — 0.20 — — — — — — — Balance F20 10.000.60 — — 0.50 — — — 0.20 — — — — — — — Balance F21 10.00 0.60 — — 0.10 —— — 0.20 — — — — 0.03 — — Balance F22 10.00 — 0.04 — 0.05 — — — 0.20 — —— — — — — Balance F23 10.00 0.01 — — 0.02 — — — 0.20 — — — — — — —Balance F24 10.00 1.50 — — 0.20 — — — 0.20 — — — — — — — Balance F25 3.50 1.50 — — 0.20 — — — 0.20 — — — — — — — Balance F26 10.00 3.50 — —0.10 — — — 0.20 — — — — — — — Balance

The prepared brazing material ingots and the core material ingots weresuperimposed in the combinations listed in Table 3. Thereafter, thecombinations were subjected to hot rolling and cold rolling andsubjected to final annealing under the conditions listed in Table 4 toacquire annealed clad materials. As other examples, the combinationswere subjected to intermediate annealing under the conditions listed inTable 4 after hot rolling and cold rolling, and thereafter subjected tocold rolling to acquire annealed clad materials. As other examples, thecombinations were subjected to intermediate annealing under theconditions listed in Table 4 after hot rolling and cold rolling,thereafter subjected to cold rolling, and thereafter subjected to finalannealing under the conditions listed in Table 4 to acquire annealedclad materials. Cleaning was executed after annealing in the caseslisted in Table 4. The final thickness was set to 0.3 to 1.0 mm. Theacquired clad sheet materials were used as test pieces.

The thickness of the oxide film on the brazing material surface of eachof the test pieces was measured by X-ray photoelectron spectroscopy(XPS). Oxygen was analyzed by XPS in the depth direction from thesurface of the material, and the position of the measured peak halfwidth of the oxygen was set as the oxide film thickness. In addition, amolar ratio (for example, Mg quantity/Al quantity) of each of Mg, Li,and Ca to aluminum (sum total of metal aluminum and aluminumcompositions in the aluminum oxide) in the oxide film thickness in termsof atom was calculated.

As the oxide film thickness, a thickness of 10 nm or less is expressedas the most preferable thickness “A”, a thickness more than 10 nm and 50nm or less is expressed as “B”, and a thickness more than 50 nm isexpressed as “C” in the column “oxide film thickness” in Table 4. In thecolumn “molar ratio”, a ratio of 0.1 or less is expressed as “A”, aratio more than 0.1 and 0.5 or less is expressed as “B”, and a ratiomore than 0.5 is expressed as “C”.

The brazability of each of the test pieces can be evaluated by executinga clearance filling test. Each of the test pieces used in the clearancefilling test was mounted with SUS jigs in a state in which a 3003 barematerial was disposed as a vertical plate and the test piece wasdisposed as a horizontal plate, and subjected to brazing in a nitrogenatmosphere in a furnace without using a flux, in the same manner asFIG. 1. As the brazing conditions, the oxygen concentration in thefurnace when the test piece temperature during temperature rising was400° C. or more was controlled to 50 ppm or less, and the oxygenconcentration when the test piece temperature was 570° C. or more wascontrolled to 10 ppm or less, and the maximum temperature of the testpiece was set to 600° C. Although the length of the vertical plate of anordinary clearance filling test (LWS T8801) is 55 mm, the length of thevertical plate of each of the present test pieces was set to 25 mm toincrease a gradient of a clearance formed between the horizontal plateand the vertical plate. In this manner, an evaluation method simulatinga heat exchanger having a large clearance was adopted.

In the clearance filling test, the brazability can be evaluated on thebasis of a length FL of fillet formed after brazing. In the column“brazability” in Table 3, the soundness of the FL and the fillet isexpressed with three levels, that is, “A” indicates the case where thelength FL was 5 mm or more and no partial fillet discontinuanceoccurred, “B” indicates the case where the length FL was 5 mm or moreand partial fillet discontinuance occurred, and “C” indicates the casewhere the length FL was less than 5 mm. Among them, “A” was determinedas a passing level.

The volume change ratio of oxide particles comprising Mg, Li, and Ca andformed after brazing to an oxide film formed before brazing heating wasdetermined by determining the volume per oxygen atom by dividing themolecular weight of the oxide by a density disclosed in the publiclyknown document, and dividing the volume per oxygen atom by the volumeper oxygen atom of the oxide film formed before brazing heating. Thefilm composition of the oxide film formed before brazing heating isAl₂O₃, and the density thereof is determined as “3.0 g/cm³”. Table 3lists analysis of the acquired clad sheet materials and performance testresults of the brazability thereof.

TABLE 3 Atomic molar ratio Oxide to Al in oxide film film Volume changeratio Brazing Core Brazing Manufacturing Molar thickness (Type of oxideNo. material 1 material material 2 condition Element ratio (nm)particles) Brazability Examples 1 F2 C1 — P5 Ca A A 0.967 (CaAl₁₂O₁₉) A2 F3 C2 — P1 Mg A A 0.863 (MgAl₂O₄) A 3 F4 C3 — P4 Mg A B 0.863(MgAl₂O₄) A 4 F5 C3 — P4 Mg A B 0.863 (MgAl₂O₄) A 5 F6 C3 — P4 Mg A B0.863 (MgAl₂O₄) A 6 F7 C3 — P6 Mg A A 0.863 (MgAl₂O₄) A 7 F8 C4 — P1 MgA A 0.863 (MgAl₂O₄) A 8 F9 C4 — P1 Mg A A 0.863 (MgAl₂O₄) A 9 F11 C4 —P1 Mg B B 0.863 (MgAl₂O₄) A 10 F12 C6 — P1 Mg B B 0.863 (MgAl₂O₄) A 11F13 C7 — P1 Mg B B 0.863 (MgAl₂O₄) A 12 F14 C7 — P1 Mg B B 0.863(MgAl₂O₄) A 13 F17 C1 — P2 Mg A B 0.863 (MgAl₂O₄) A 14 F18 C1 — P3 Mg AB 0.863 (MgAl₂O₄) A 15 F20 C1 — P1 Mg B B 0.863 (MgAl₂O₄) A 16 F21 C9 —P1 Mg B B 0.863 (MgAl₂O₄) A 17 F22 C8 — P1 Li A A 0.822 (LiAl₅O₈) A 18F24 C11 F24 P1 Mg A B 0.863 (MgAl₂O₄) A 19 F24 C13 — P6 Mg A A 0.863(MgAl₂O₄) A Comparative 101 F25 C12 — P1 Mg A A 0.863 (MgAl₂O₄) Cexamples 102 F1 C1 Edge crack occurred in hot rolling of brazingmaterial and manufacturing was impossible 103 F23 C10 P1 Mg A B 0.863(MgAl₂O₄) C 104 F26 C12 — P1 Mg C C 0.994 (MgO) C

TABLE 4 Annealing condition Oxygen concentration Dew point Condition inatmosphere in atmosphere Acid number (ppm) (° C.) cleaning P1 10,000 orless 20 or less Not executed P2 500 or less 0 or less Not executed P3100 or less −10 or less Not executed P4 10,000 or less 10 or less Afterintermediate annealing P5 10,000 or less 10 or less After finalannealing P6 10,000 or less 10 or less After intermediate annealing andafter final annealing

1-16. (canceled)
 17. An aluminum alloy brazing sheet used for brazing inan inert gas atmosphere without using a flux, the aluminum alloy brazingsheet comprising: a brazing material cladded onto at least one sidesurface of a core material, the core material being formed of aluminumor an aluminum alloy core material comprising any one or two or more ofFe of 1.50 mass % or less, Si of 1.50 mass % or less, Cu of 2.00 mass orless, Mn of 2.00 mass % or less, Zn of 3.00 mass % or less, Cr of 0.30mass % or less, Ti of 0.30 mass % or less, Zr of 0.30 mass % or less, Inof 0.10 mass % or less, and Sn of 0.10 mass % or less, and optionallyany one or two or more of Mg of 3.00 mass % or less, Li of 3.00 mass %or less, Ca of 3.00 mass % or less, and Bi of 1.00 mass % or less, withthe balance being aluminum and inevitable impurities, the brazingmaterial being an aluminum alloy brazing material comprising Si of 4.00to 13.00 mass %, and any one or two or more of Mg more than 0.03 mass %and 3.00 mass % or less, Li more than 0.03 mass % and 3.00 mass % orless, and Ca more than 0.03 mass % and 3.00 mass or less, and optionallyany one or two or more of Bi of 1.00 mass % or less, Na of 0.05 mass %or less, Sr of 0.05 mass % or less, Sb of 0.05 mass % or less, Zn of8.00 mass % or less, Cu of 4.00 mass % or less, Fe of 1.00 mass % orless, Mn of 1.00 mass % or less, Cr of 0.30 mass % or less, Ti of 0.30mass % or less, Zr of 0.30 mass % or less, In of 0.10 mass % or less,and Sn of 0.10 mass or less, with the balance being aluminum andinevitable impurities, wherein an oxide is formed on a surface of thealuminum alloy brazing sheet by brazing heating, the oxide including anyone or two or more of Mg, Li, and Ca and having a volume change ratio of0.990 or less to a surface oxide film formed before brazing heating, andan atomic molar ratio of Mg, Li, and Ca to Al in the oxide formed on thesurface of the aluminum alloy brazing sheet before brazing heating is0.5 or less.
 18. The aluminum alloy brazing sheet according to claim 17,wherein the aluminum alloy brazing sheet is a two-layer material inwhich the brazing material is cladded onto one side surface of the corematerial.
 19. The aluminum alloy brazing sheet according to claim 17,wherein the aluminum alloy brazing sheet is a three-layer material inwhich the brazing material is cladded onto each of both side surfaces ofthe core material.
 20. The aluminum alloy brazing sheet according toclaim 17, wherein the aluminum alloy brazing sheet is a three-layermaterial in which the brazing material is cladded onto one side surfaceof the core material and a cladding material is cladded onto the otherside surface of the core material, and the cladding material is analuminum alloy cladding material formed of aluminum or an aluminum alloycomprising Zn of 6.00 mass % or less, and optionally any one or two ormore of Mn of 2.00 mass % or less, Mg of 3.00 mass % or less, Si of 5.00mass % or less, Fe of 1.50 mass % or less, Cu of 1.00 mass % or less, Tiof 0.30 mass % or less, Zr of 0.30 mass % or less, Cr of 0.30 mass % orless, In of 0.10 mass % or less, and Sn of 0.10 mass % or less, with thebalance being aluminum and inevitable impurities.
 21. The aluminum alloybrazing sheet according to claim 17, wherein the oxide formed on abrazing material surface of the aluminum alloy brazing sheet has athickness of 50 nm or less.
 22. The aluminum alloy brazing sheetaccording to claim 18, wherein the oxide formed on a brazing materialsurface of the aluminum alloy brazing sheet has a thickness of 50 nm orless.
 23. The aluminum alloy brazing sheet according to claim 19,wherein the oxide formed on a brazing material surface of the aluminumalloy brazing sheet has a thickness of 50 nm or less.
 24. The aluminumalloy brazing sheet according to claim 20, wherein the oxide formed on abrazing material surface of the aluminum alloy brazing sheet has athickness of 50 nm or less.
 25. A method for manufacturing an aluminumalloy brazing sheet, the method comprising executing at least hotworking and cold working for (1) a stacked structure acquired bystacking a brazing material ingot and a core material ingot in thisorder; (2) a stacked structure acquired by stacking a brazing materialingot, a core material ingot, and a brazing material ingot in thisorder; or (3) a stacked structure acquired by stacking a brazingmaterial ingot, a core material ingot, and a cladding material ingot inthis order, to acquire an aluminum alloy brazing sheet, wherein the corematerial ingot is formed of aluminum or an aluminum alloy comprising anyone or two or more of Fe of 1.50 mass % or less, Si of 1.50 mass % orless, Cu of 2.00 mass % or less, Mn of 2.00 mass % or less, Zn of 3.00mass % or less, Cr of 0.30 mass % or less, Ti of 0.30 mass % or less, Zrof 0.30 mass % or less, In of 0.10 mass % or less, and Sn of 0.10 mass %or less, and optionally any one or two or more of Mg of 3.00 mass % orless, Li of 3.00 mass % or less, and Ca of 3.00 mass % or less, with thebalance being aluminum and inevitable impurities, the brazing materialingot is formed of an aluminum alloy comprising Si of 4.00 to 13.00 mass%, and any one or two or more of Mg more than 0.03 mass % and 3.00 mass% or less, Li more than 0.03 mass % and 3.00 mass % or less, and Ca morethan 0.03 mass % and 3.00 mass % or less, and optionally any one or twoor more of Na of 0.05 mass % or less, Sr of 0.05 mass % or less, Sb of0.05 mass % or less, Zn of 8.00 mass % or less, Cu of 4.00 mass % orless, Fe of 1.00 mass or less, Mn of 1.00 mass % or less, Cr of 0.30mass % or less, Ti of 0.30 mass % or less, Zr of 0.30 mass % or less, Inof 0.10 mass % or less, and Sn of 0.10 mass % or less, with the balancebeing aluminum and inevitable impurities, the cladding material ingot isformed of aluminum or an aluminum alloy comprising Zn of 6.00 mass % orless, and optionally any one or two or more of Mn of 2.00 mass % orless, Mg of 3.00 mass % or less, Si of 5.00 mass % or less, Fe of 1.50mass % or less, Cu of 1.00 mass % or less, Ti of 0.30 mass % or less, Zrof 0.30 mass % or less, Cr of 0.30 mass % or less, In of 0.10 mass orless, and Sn of 0.10 mass % or less, with the balance being aluminum andinevitable impurities, and intermediate annealing, final annealing, orannealing is executed, the intermediate annealing being executed betweenrolling passes in the cold working to heat the stacked structure at 250to 450° C. for one hour or more in an atmosphere controlled to have anoxygen concentration of 10,000 ppm or less and a dew point of 20° C. orless, the final annealing being executed after a last pass of the coldworking to heat the stacked structure at 250 to 450° C. for one hour ormore in an atmosphere controlled to have an oxygen concentration of10,000 ppm or less and a dew point of 20° C. or less, and the annealingbeing executed both between rolling passes in the cold working and afterthe last pass of the cold working to heat the stacked structure at 250to 450° C. for one hour or more in an atmosphere controlled to have anoxygen concentration of 10,000 ppm or less and a dew point of 20° C. orless.
 26. The method for manufacturing an aluminum alloy brazing sheetaccording to claim 25, wherein one of the core material ingot and thebrazing material ingot further comprises Bi of 1.0 mass % or less. 27.The method for manufacturing an aluminum alloy brazing sheet accordingto claim 25, wherein a brazing material surface of a clad material issubjected to etching using one or both of an acid aqueous solution andan alkaline aqueous solution, the etching being executed after theintermediate annealing when the intermediate annealing is executed,after the final annealing when the final annealing is executed, and oneor both of timing after the intermediate annealing and timing after thefinal annealing when both the intermediate annealing and the finalannealing are executed.
 28. The method for manufacturing an aluminumalloy brazing sheet according to claim 26, wherein a brazing materialsurface of a clad material is subjected to etching using one or both ofan acid aqueous solution and an alkaline aqueous solution, the etchingbeing executed after the intermediate annealing when the intermediateannealing is executed, after the final annealing when the finalannealing is executed, and one or both of timing after the intermediateannealing and timing after the final annealing when both theintermediate annealing and the final annealing are executed.